DUBLIN — A firebomb detonated Friday in a hotel lobby in the Northern Ireland city of Londonderry, but police said a swift midnight evacuation ensured that nobody was injured.

The bomb exploded inside the Everglades Hotel in Northern Ireland’s second-largest city. Witnesses said a masked man tossed a bag beside the hotel’s reception desk, said he was from the IRA, and warned that a bomb inside the bag would explode in 30 minutes.

‘‘Someone set off the fire alarm and I called the police,’’ said Gary Rutherford, who had just dropped off relatives at the hotel. ‘‘It was quite confusing at the time for most of the guests because they were in bed. It was mayhem.’’


As British Army specialists were deploying a robot to examine the bomb, it exploded and sent flames cascading throughout the evacuated lobby. Nobody was injured.

Analysts noted that the hotel last week hosted a police recruitment drive for more applicants from the city’s mostly Catholic population, a peacemaking goal bitterly opposed by IRA activists.